The present invention relates in general to liquid level monitors and controllers, and in particular to an electronic liquid level monitor and control assembly compatible for integration into, for example, a digital microcomputer system which controls a multiple-cycle clothes washing machine.
The continued utilization of microcomputer control systems in place of conventional electromechanical control systems has necessitated a concurrent development of input/output hardware which is compatible with the newly adopted microcomputer systems.
For example, the successful adaptation of a microcomputer control system to a clothes washing machine required that the transducer or transducers monitoring the water level in the washtub provide a compatible digital input to the associated microcomputer control system.
U.S. Pat. No. 4,084,237 to Beachem et al discloses a microcomputer control system for a clothes washing machine wherein the washtub water level is monitored by two transducer-like ON-OFF fluid pressure switches. While such switches inherently provide the necessary digital input characteristics compatible with a microcomputer system, they are disadvantageous in that a switch must be provided for each level of washtub water desired to be monitored and controlled via the microcomputer system. Thus, the controlled level of washtub water as taught by Beachem et al is limited to only two levels, that is, a high water level and a low water level.
It has been recognized that a single transducer washtub water level monitor and controller providing a quantitative analog-type measurement of water level in a digital format would provide greater wash cycle program flexibility as opposed to the qualitative ON-OFF liquid level indications noted previously with regard to Beachem et al. For example, four increasing water levels for use with small, medium, normal, and extra large wash loads could be provided for without the necessity of four separate ON-OFF fluid pressure switches.
The provision of such an analog-to-digital type liquid level monitor for use with a microcomputer controlled clothes washing machine must meet stringent cost and reliability requirements necessitated by the highly competitive appliance business.